Research undertaken for Seafish and AHDB's Enjoy Fish & Chips campaign found a huge disparity in portion sizes at 600 fish and chip outlets around the UK.
Currently a medium portion of cod varies from 93g to 562g and a medium portion of chips varies from 100g to 797g, while the average price of fish and chips only varies by 34 per cent region by region.
Under Seafish and AHDB's recommendations, a medium, or regular portion of fish and chips would be 170g (fish) and 284g (chips).
Tom Pickerell, technical director at Seafish, said giving guidance about portion sizes had two main benefits.
"Firstly, by standardising portion sizes across the industry, consumers will know what to expect when ordering their selected portion size, wherever they are in the UK," he said.
“Secondly, it’s about choice. By offering a greater selection of sizes shops can potentially open themselves up to increased business from lunch time trade and by upselling single smaller portions, rather than a large shared portion.”
Standardising portion sizes is also expected to help foodservice businesses cut waste, improve the bottom line and provide more clarity around nutritional information, said Seafish and AHDB.
Rob Clayton, sector strategy director at AHDB Potatoes added: “One of the key findings of the research suggested that one in three consumers said a greater range of portion sizes would encourage them to eat fish and chips more often. That's more than 17 million people across the UK.
“Couple this with the fact that 45 percent of people would order smaller portions to cut their calorie intake and there is a huge potential marketplace for outlets to encourage health conscious consumers through their doors.”
Enjoy Fish & Chips guidance on portion sizes:
Operators can find more information about portion sizes as well as the 'perfect serve' tool to show cost savings at the Enjoy Fish & Chips website.